Controller area network with flexible data-rate

ABSTRACT

A method for serially communicating by exchanging data frames between a transmitting and at least one receiving node connected by a bus, transmit/receive roles being assigned to nodes for each data frame by the CAN ISO 11898-1 (“CAN”) arbitration procedure, exchanged data frames having a structure based on CAN, data frames being a bit sequence, the structure of the data frames including a Start-Of-Frame-Bit, and Fields for Arbitration, Control, Data, CRC, Acknowledge, and End-Of-Frame, the Data Field may have a zero-bit length, other Fields containing at least two bits, each having a bit time divided into Time Segments, the bit-rate defined by the bit time&#39;s reciprocal value, for at least one first predeterminable part of the exchanged data frames the bit-rate lies below 1 Mbit/s, for at least one second predeterminable part the bit-rate lies higher, at least two different Time Segment value sets being predeterminable for each part.

FIELD OF THE INVENTION

The present invention relates to a method for serially communicating byexchanging data frames between a transmitting and at least one receivingnode connected by a bus system.

BACKGROUND INFORMATION

The acceptance and introduction of serial communication to more and moreapplications has led to requirements that the bandwidth for the serialcommunication needs to be increased.

Two factors limit the effective data-rate in CAN networks, first theminimum bit time required for the function of the CAN bus arbitrationmethod and second the relation between the numbers of data bits andframe bits in a CAN message.

The following parts of the CAN protocol specification (Version 2.0,Robert Bosch GmbH, 1991) apply unchanged in the CAN FD protocol:

-   -   Definition of TRANSMITTER/RECEIVER    -   MESSAGE FILTERING    -   MESSAGE VALIDATION    -   CODING    -   ERROR HANDLING    -   Error Detection    -   Error Signaling    -   FAULT CONFINEMENT

SUMMARY OF THE INVENTION

A new protocol is described that is based on the CAN protocol asspecified in ISO 11898-1 and is called “CAN with Flexible Data-Rate” orCAN FD. It still uses the CAN bus arbitration method, it increases thebit-rate by switching to a shorter bit time after the end of thearbitration process and returns to the longer bit time at the CRCDelimiter, before the receivers send their acknowledge bits. Theeffective data-rate is increased by allowing longer data fields. CANuses four bits as Data Length Code resulting in 16 different codes, butonly the first nine values are used, codes [0-8] standing for data fieldlength of [0-8] bytes. In CAN, the codes [9-15] are defined to signifyeight data bytes. In CAN FD, the codes are used to signify longer datafields.

In particular, a method is described for the serial communication byexchange of data frames between a transmitting node and at least onereceiving node who are connected by a bus system is described, whereinthe roles of transmitter and receiver are assigned to nodes for eachdata frame by the arbitration procedure defined in the CAN-Standard ISO11898-1, wherein the exchanged data frames have a logical structureaccording to the CAN-Standard ISO 11898-1, wherein the data frames arecomposed of a sequence of bits, wherein the logical structure of thedata frames includes a Start-Of-Frame-Bit, an Arbitration Field, aControl Field, a Data Field, a CRC Field, an Acknowledge Field and anEnd-Of-Frame Field, wherein the Data Field may have a length of zerobits, wherein each other Field contains at least two bits, wherein eachbit has a bit time, wherein each bit time is divided into Time Segments(SYNC_SEG, PROP_SEG, PHASE_SEG1, PHASE_SEG2), wherein the bit-rate isdefined by the reciprocal value of the bit time, wherein for at leastone first predeterminable part of the exchanged data frames the bit-ratein that part lies below a maximum value of 1 Mbit/s, wherein for atleast one second predeterminable part of the exchanged data frames thebit-rate in that part lies higher than in the at least one firstpredeterminable part, characterized in that at least two different setsof values of the Time Segments (SYNC_SEG, PROP_SEG, PHASE_SEG1,PHASE_SEG2) are predeterminable for the at least two different parts ofthe exchanged data frames.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a CAN FD frame.

FIG. 2 shows the position where the bit-rate is switched within amessage.

FIG. 3 shows the coding of the number of data bytes by the DATA LENGTHCODE.

FIG. 4 shows that the CRC FIELD contains the CRC SEQUENCE followed by aCRC DELIMITER.

FIG. 5 shows that the ACK FIELD is two or three bits long and containsthe ACK SLOT and the ACK DELIMITER.

FIG. 6 shows the bit time, where both bit times consist of separatenon-overlapping time segments, namely, SYNCHRONIZATION SEGMENT(SYNC_SEG), PROPAGATION TIME SEGMENT (PROP_SEG), PHASE BUFFER SEGMENT1(PHASE_SEG1), and PHASE BUFFER SEGMENT2 (PHASE_SEG2).

DETAILED DESCRIPTION

The following describes a method for the serial communication byexchange of data frames between a transmitting node and at least onereceiving node who are connected by a bus system is described, whereinthe roles of transmitter and receiver are assigned to nodes for eachdata frame by the arbitration procedure defined in the CAN-Standard ISO11898-1, wherein the exchanged data frames have a logical structureaccording to the CAN-Standard ISO 11898-1, wherein the data frames arecomposed of a sequence of bits, wherein the logical structure of thedata frames includes a Start-Of-Frame-Bit, an Arbitration Field, aControl Field, a Data Field, a CRC Field, an Acknowledge Field and anEnd-Of-Frame Field, wherein the Data Field may have a length of zerobits, wherein each other Field contains at least two bits, wherein eachbit has a bit time, wherein each bit time is divided into Time Segments(SYNC_SEG, PROP_SEG, PHASE_SEG1, PHASE_SEG2), wherein the bit-rate isdefined by the reciprocal value of the bit time, wherein for at leastone first predeterminable part of the exchanged data frames the bit-ratein that part lies below a maximum value of 1 Mbit/s, wherein for atleast one second predeterminable part of the exchanged data frames thebit-rate in that part lies higher than in the at least one firstpredeterminable part, characterized in that at least two different setsof values of the Time Segments (SYNC_SEG, PROP_SEG, PHASE_SEG1,PHASE_SEG2) are predeterminable for the at least two different parts ofthe exchanged data frames.

The CAN systems can migrate gradually to CAN FD systems. All nodes inthe network must have a CAN FD protocol controller for CAN FDcommunication, but all CAN FD protocol controllers are also able to takepart in standard CAN communication. If the CAN FD communication islimited to data fields with a length of up to eight data bytes, it isnot necessary to change the application program apart from the initialconfiguration of the controller.

The Controller Area Network (CAN) is a serial communications protocolwhich efficiently supports distributed realtime control with a very highlevel of security. Its domain of application ranges from high speednetworks to low cost multiplex wiring. In automotive electronics, enginecontrol units, sensors, anti-skid-systems, etc. are connected using CANwith bitrates up to 1 Mbit/s. At the same time it is cost effective tobuild into vehicle body electronics, e.g. lamp clusters, electricwindows etc. to replace the wiring harness otherwise required.

The CAN FD (CAN with Flexible Data-Rate) complements CAN in applicationsthat require a higher data-rate. The CAN FD protocol controllers arealso able to take part in standard CAN communication, making it possibleto use CAN FD only in specific operation modes, e.g. software-downloadat end-of-line or maintenance. CAN FD requires two sets of bit timingconfiguration registers, one bit time for the arbitration phase and onebit time for the data field. The bit time for the arbitration phase hasthe same limitations as in standard CAN networks, the bit time for thedata field is chosen with regard to the performance of the chosentransceiver and the characteristics of the CAN FD network.

Standard CAN transceivers can be used for CAN FD, dedicated transceiversare optional. CAN FD protocol controllers may provide additionalinterface signals to switch—in the phase with higher bit-rate—adedicated CAN FD transceiver into an alternate operating mode.

Dedicated CAN FD transceivers may use an alternate coding system in thephase with higher bit-rate, not restricted to CAN's NRZ coding.

A CAN FD frame consists of the same elements as a CAN frame, thedifference is that in a CAN FD frame, the Data Field and the CRC Fieldmay be longer. Message validation requires, as in CAN, a dominantAcknowledge bit from at least one receiver. The CAN FD fault confinementwith Error Frames, Error Counters, Error Passive level and Bus-Off levelis the same as in CAN, it is based on the same five error types: BitError, Stuff Error, CRC Error, Form Error, and Acknowledgement Error.

An example of a CAN FD frame is pictured in FIG. 1.

CAN FD frames have the same structure as CAN frames, the differentiationbetween CAN frames and CAN FD frames is at the reserved bit immediatelybefore the Data Length Code in the Control Field. In a CAN FD frame,this bit is transmitted recessive.

The first part of a CAN FD frame, until the reserved bit thatdistinguishes the protocols, is transmitted with the same bit-rate as aCAN frame. The bit-rate is switched after the reserved bit until the CRCDelimiter is reached or until the CAN FD controller sees an errorcondition that results in the starting of an Error Frame. CAN FD ErrorFrames, as well as ACK Field, End of Frame, and Overload Frames aretransmitted with the same bit-rate as a CAN Error Frame.

Frame Format:

FIG. 2 shows the position where the bit-rate is switched within amessage.

CAN FD supports both Identifier lengths of the CAN protocol, the 11 bitlong “Standard Format” and the 29 bit long “Extended Format”. In bothcases, the bit-rate is switched to the shorter bit time at the reservedbit r0 (before the DLC).

The number of bytes in the DATA FIELD is indicated by the DATA LENGTHCODE. This DATA LENGTH CODE is 4 bits wide and is transmitted within theCONTROL FIELD.

The coding of the DATA LENGTH CODE is different in CAN FD. The firstnine codes are the same, but the following codes, that in CAN specify aDATA FIELD of eight bytes, specify longer DATA FIELDS in CAN FD. AllRemote Frames shall use a DATA LENGTH CODE of zero, regardless of theDATA LENGTH CODE of the corresponding Data Frame.

Note: The maximum length of the DATA FIELD is specified to be 64 bytes.This value, and the other values >8 of DATA LENGTH CODE may change inthe final specification of CAN FD.

The coding of the number of data bytes by the DATA LENGTH CODE isdescribed in FIG. 3.

The CRC FIELD contains the CRC SEQUENCE followed by a CRC DELIMITER, asshown in FIG. 4.

CRC SEQUENCE: The frame check sequence is derived from a cyclicredundancy code (BCH Code).

In order to carry out the CRC calculation the polynomial to be dividedis defined as the polynomial, the coefficients of which are given by therelevant bit stream. CAN FD uses different CRC polynomials for differentframe length. For frames with up to eight data bytes, the samepolynomial as in CAN is used.

For frames with up to eight data bytes, the relevant bit stream is thedestuffed bit stream consisting of START OF FRAME, ARBITRATION FIELD,CONTROL FIELD, DATA FIELD (if present) and, for the 15 lowestcoefficients, by 0. This polynomial is divided (the coefficients arecalculated modulo-2) by the generator-polynomial, which, with a HammingDistance HD=6, is best suited for frames with bit counts less than 127bits:X15+X14+X10+X8+X7+X4+X3+1.

For frames with more than eight bytes in the DATA FIELD, different (andlonger) CRC polynomials are used, adapted to the length of the frame.The CRC Field is lengthened accordingly. In longer frames, also thestuff bits that occur before the CRC SEQUENCE shall be protected by theCRC.

Each CRC SEQUENCE is calculated in a separate shift register block. Atthe start of the frame, in all nodes all CRC SEQUENCES shall becalculated concurrently, until after the arbitration one of the CRCSEQUENCES is selected by the reserved bit and by the DLC. Only theselected CRC SEQUENCE can cause a CRC Error.

Note: The actual CRC polynomials will be defined after the coding of theDATA LENGTH CODE is finalized.

CRC DELIMITER: The CRC SEQUENCE is followed by the CRC DELIMITER whichconsists of one or two ‘recessive’ bits. A transmitter shall send onlyone ‘recessive’ bit as CRC Delimiter but all nodes shall accept two‘recessive’ bits before the edge from recessive to dominant that startsthe Acknowledge Slot. Note: When the CRC Delimiter is detected, the CANFD protocol controllers switch back to the bit-rate with the longer bittime.

The phase-shift between the nodes in a CAN network is defined by thedelay times in the transceivers and the propagation time on the CAN busline. The phase-shift is the same in CAN and in CAN FD, but it isproportionally larger in the phase with the shorter bit time. Allreceivers in the network may have a different phase-shift to thetransmitter, since they see the transmitted edges at different times. Tocompensate for these phase-shifts when the bit-rate is switched back tothe longer bit time, one additional bit time tolerance is allowed beforeand after the edge from recessive to dominant that starts theAcknowledge Slot.

The ACK FIELD is two or three bits long and contains the ACK SLOT andthe ACK DELIMITER, as shown in FIG. 5. In the ACK FIELD the transmittingstation sends two ‘recessive’ bits. A RECEIVER which has received avalid message correctly, reports this to the TRANSMITTER by sending a‘dominant’ bit during the ACK SLOT (it sends ‘ACK’).

ACK SLOT: All stations having received the matching CRC SEQUENCE reportthis within the ACK SLOT by superscribing the ‘recessive’ bit of theTRANSMITTER by a ‘dominant’ bit. To compensate for phase shifts betweenthe receivers, all nodes accept a two bit long ‘dominant’ phase ofoverlapping ACK bits as a valid ACK.

ACK DELIMITER: The ACK DELIMITER is the second or third bit of the ACKFIELD and has to be a ‘recessive’ bit. As a consequence, the ACK SLOT issurrounded by two ‘recessive’ bits (CRC DELIMITER, ACK DELIMITER).

END OF FRAME: Each DATA FRAME and REMOTE FRAME is delimited by flagsequence consisting of seven ‘recessive’ bits.

CAN Protocol Features in CAN FD:

The following parts of the CAN protocol specification (Version 2.0,Robert Bosch GmbH, 1991) apply unchanged in the CAN FD protocol:

-   -   Definition of TRANSMITTER/RECEIVER    -   MESSAGE FILTERING    -   MESSAGE VALIDATION    -   CODING    -   ERROR HANDLING    -   Error Detection    -   Error Signaling    -   FAULT CONFINEMENT

Bit Timing Requirements:

The CAN FD protocol defines two bit-rates, the first bit-rate with alonger bit time and the second bit-rate with a shorter bit time. Thedefinition for the first bit-rate is the same as for the NOMINAL BITRATE and the NOMINAL BIT TIME in the CAN protocol specification. Thedefinition for the second bit-rate requires a separate configurationregister set. Both bit times consist of separate non-overlapping timesegments, these segments

-   -   SYNCHRONIZATION SEGMENT (SYNC_SEG)    -   PROPAGATION TIME SEGMENT (PROP_SEG)    -   PHASE BU FFER SEGMENT1 (PHASE_SEG1)    -   PHASE BU FFER SEGMENT2 (PHASE_SEG2)

form the bit time as shown in FIG. 6.

The time segments for the two bit rates of the CAN FD protocol aredefined by two sets of configuration registers.

SYNC SEG: This part of the bit time is used to synchronize the variousnodes on the bus. An edge is expected to lie within this segment.

PROP SEG: This part of the bit time is used to compensate for thephysical delay times within the network. It is twice the sum of thesignal's propagation time on the bus line, the input comparator delay,and the output driver delay.

PHASE SEG1, PHASE SEG2: These Phase-Buffer-Segments are used tocompensate for edge phase errors. These segments can be lengthened orshortened by resynchronization.

SAMPLE POINT: The SAMPLE POINT is the point of time at which the buslevel is read and interpreted as the value of that respective bit. It'slocation is at the end of PHASE_SEG1.

INFORMATION PROCESSING TIME: The INFORMATION PROCESSING TIME is the timesegment starting with the SAMPLE POINT reserved for calculation thesubsequent bit level.

The length of the time segments is defined in integer multiples of theTIME QUANTUM, with the TIME QUANTUM is a fixed unit of time derived fromthe oscillator period. There exists a programmable prescaler, withintegral values, ranging at least from 1 to 32. Starting with theMINIMUM TIME QUANTUM, the TIME QUANTUM can have a length ofTIME QUANTUM(n)=m(n)*MINIMUM TIME QUANTUM

with m the value of the prescaler. Two values for the prescaler, m(1)and m(2) are defined the CAN FD protocol, one for each bit-rate,resulting in two different lengths of the TIME QUANTUM.

Length of Time Segments for the first bit-rate:

-   -   SYNC_SEG(1) is 1 TIME QUANTUM(1) long.    -   PROP SEG(1) is programmable to be 1, 2, . . . , 8 TIME QUANTA(1)        long.    -   PHASE_SEG1(1) is programmable to be 1, 2, . . . , 8 TIME        QUANTA(1) long.    -   PHASE_SEG2(1) is the maximum of PHASE_SEG1(1) and the        INFORMATION PROCESSING TIME    -   The INFORMATION PROCESSING TIME is less than or equal to 2 TIME        QUANTA(1) long.

Length of Time Segments for the second bit-rate

-   -   SYNC_SEG(2) is 1 TIME QUANTUM(2) long.    -   PROP_SEG(2) is programmable to be 0, 1, 2, . . . , 8 TIME        QUANTA(2) long.    -   PHASE_SEG1(2) is programmable to be 1, 2, . . . , 8 TIME        QUANTA(2) long.    -   PHASE_SEG2(2) is the maximum of PHASE_SEG1(2) and the        INFORMATION PROCESSING TIME    -   The INFORMATION PROCESSING TIME is less than or equal to 2 TIME        QUANTA long.

The total number of TIME QUANTA in a bit time has to be programmable atleast from 8 to 25.

The position of the SAMPLE POINT may differ in the two bit timingconfigurations, the length of the PROP_SEG may be reduced in theconfiguration for the second bit-rate.

CAN FD Implementation:

CAN FD protocol implementations shall provide the same controller-hostinterfaces as CAN protocol implementations to provide an easy migrationpath for existing CAN applications. The minimum required differences arenew configuration registers for the CAN FD operation.

The CAN FD protocol allows frames with more than eight data bytes. It isnot required that all CAN FD implementations support longer frames, CANFD implementations may be limited to a subset of DATA FIELD length. ACAN FD implementation that supports only up to e.g. eight data bytes ina frame shall not treat received longer frames as an error, fault-freelonger frames shall be acknowledged and shall take part in acceptancefiltering. Received data bytes that exceed the CAN FD's data handlingcapacity shall be discarded. A such limited CAN FD implementation thatis requested to transmit a longer frame shall fill up the data bytes inthe frame that exceed the data handling capacity with a constant bytepattern. This pattern shall be chosen so that it does not cause theinsertion of STUFF BITS, e.g. 0x33.

The following optional interface registers provide an extended analysisof the ongoing communication:

-   -   Double set of status registers to distinguish between messages        and errors occurring while operating in the first or in the        second bit-rate.    -   Dedicated error counter to compare error rates in the two        operating modes.    -   Per message status flag indicating whether a message was        received using the first or the second bit rate.    -   Per message configuration flag controlling whether a message is        to be transmitted using the first or the second bit rate.    -   Communication management state machine that enables or disables        the use of the second bit-rate according criteria like e.g.:        Relative error rates in the two bit-rates, reception of message        in specific bit-rate, control message received from external bus        master, command written by local host.

The invention claimed is:
 1. A method for providing serial communicationby exchange of data frames between a transmitting node and at least onereceiving node, which are connected by a bus system, the methodcomprising: assigning the roles of transmitter and receiver to nodes foreach of the data frames by an arbitration procedure defined inCAN-Standard ISO 11898-1, wherein the exchanged data frames have alogical structure according to the CAN-Standard ISO 11898-1, wherein thedata frames are composed of a sequence of bits, wherein the logicalstructure of the data frames includes a Start-Of-Frame-Bit, anArbitration Field, a Control Field, a Data Field, a CRC Field, anAcknowledge Field and an End-Of-Frame Field, wherein the Data Field mayhave a length of zero bits, wherein each of the Arbitration Field, theControl Field, the CRC Field, the Acknowledge Field and the End-Of-FrameField contains at least two bits, wherein each bit has a bit time,wherein each bit time is divided into Time Segments, including SYNC_SEG,PROP_SEG, PHASE_SEG1, PHASE_SEG2, wherein bit-rate is defined byreciprocal value of the bit time, wherein for at least one firstpredeterminable part of the exchanged data frames the bit-rate in thatpart lies below a maximum value of 1 Mbit/s, wherein for at least onesecond predeterminable part of the exchanged data frames the bit-rate inthat part lies higher than in the at least one first predeterminablepart; and predetermining at least two different sets of values of theTime Segments (SYNC_SEG, PROP_SEG, PHASE_SEG1, PHASE_SEG2) for the atleast two different parts of the exchanged data frames.
 2. The method ofclaim 1, wherein in at least one of the at least two different sets ofvalues of the Time Segments, including SYNC_SEG, PROP_SEG, PHASE_SEG1,PHASE_SEG2, a value of PROP_SEG may deviate from the range of valuesspecified in the CAN Standard ISO 11898-1 and in particular may have avalue of zero.
 3. The method of claim 1, wherein the exchanged dataframes with at least two different bit times are distinguishable fromdata frames with uniform bit times by the reserved bit (r0) contained inthe Control Field.
 4. The method of claim 1, wherein the at least onesecond predeterminable part with shorter bit time of an exchanged dataframe starts with the reserved bit (r0) and ends with the recessive bit(CRC DELIMITER) at the end of the CRC Field or with the detection of anerror condition that results in the starting of an Error Frame.
 5. Themethod of claim 1, wherein exchanged data frames with at least twodifferent bit times may contain a Data Field of a size of more thaneight byte, wherein the size of the Data Field is specified by the DataLength Code contained in the Control Field, wherein a different codingfor the Data Length Code is used than the one defined in theCAN-Standard ISO 11898-1.
 6. The method of claim 5, wherein thedifferent coding for the Data Length Code is such, that the valuesbetween 0b0000 and 0b1000 correspond to data fields of zero to eightbytes as in the CAN-Standard ISO 11898-1, and that the values between0b1001 and 0b1111 correspond to data fields larger than eight bytes. 7.The method of claim 5, wherein the content of the CRC Field for at leastthe exchanged data frames with a size of the Data Field of more thaneight byte is determined using a different CRC polynomial than the onedefined in the CAN-Standard ISO 11898-1.
 8. The method of claim 5,wherein the size of the CRC Field for at least the exchanged data frameswith a size of the Data Field of more than eight byte is different fromthe one defined in the CAN-Standard ISO 11898-1.
 9. The method of claim5, wherein starting with the Start-Of-Frame-Bit at least two CRCsequences are calculated concurrently, until after the arbitration oneof the CRC sequences is selected by the reserved bit (r0) and by theData Length Code to be the valid CRC sequence which can cause a CRCError.
 10. The method of claim 1, wherein a transmitter sends onerecessive bit (CRC DELIMITER) after the CRC sequence and all nodesaccept two recessive bits before the change of the bus state that startsthe ACK SLOT without detecting an error.
 11. The method of claim 1,wherein a receiver which has received the matching CRC sequence sends adominant bit (ACK) within the ACK SLOT and all nodes accept a two bitlong dominant bus state of overlapping ACK bits without detecting anerror.
 12. The method of claim 1, wherein the at least two different bittimes in the exchanged data frames are produced by using two differentvalues of the prescaler, wherein the prescaler is defined as the ratiobetween TIME QUANTUM and MINIMUM TIME QUANTUM.
 13. The method of claim1, wherein in the at least one second predeterminable part of theexchanged data frames, where the bit time of the bits is shorter than inthe at least one first predeterminable part, a different bit codingmethod is used than in the at least one first predeterminable part. 14.A system for providing serial communication by exchange of data framesbetween nodes which are connected by a bus system, comprising: atransmitter node and a receiving node, wherein roles of transmitter andreceiver are assigned to nodes for each data frame by an arbitrationprocedure defined in the CAN-Standard ISO 11898-1, wherein the exchangeddata frames have a logical structure according to the CAN-Standard ISO11898-1, wherein the data frames are composed of a sequence of bits,wherein the logical structure of the data frames includes aStart-Of-Frame-Bit, an Arbitration Field, a Control Field, a Data Field,a CRC Field, an Acknowledge Field and an End-Of-Frame Field, wherein theData Field may have a length of zero bits, wherein each of theArbitration Field, the Control Field, the CRC Field, the AcknowledgeField and the End-Of-Frame Field contains at least two bits, whereineach bit has a bit time, wherein each bit time is divided into TimeSegments, including SYNC_SEG, PROP_SEG, PHASE_SEG1, PHASE_SEG2, whereinbit-rate is defined by reciprocal value of the bit time, wherein for atleast one first predeterminable part of the exchanged data frames thebit-rate in that part lies below a maximum value of 1 Mbit/s, whereinfor at least one second predeterminable part of the exchanged dataframes the bit-rate in that part lies higher than in the at least onefirst predeterminable part; and wherein at least two different sets ofvalues of the Time Segments including SYNC_SEG, PROP_SEG, PHASE_SEG1,and PHASE_SEG2 are predetermined, for the at least two different partsof the exchanged data frames.